Alternating-current motor.



No. 872,559. PATENTBD DEC 3, 1907.

- F. EIGHBBRG.

ALTERNATING CURRENT MOTOR.

APPLIOA'HOI FILED DBO. ll, 1006.

W/ nesses: Inventor.-

M W F/Gdf/Ch E/chbergt m W Q4: :3.

- ture short-circuit acts UNITED STATES PATENT OFFICE.

Fltll-llHtlUll l'llUlllllCRO, Ol" lll'lltlllN, GERMANY, ASHIUNOR 'lO GENERAL J'IL'IIUTRIU OOMIANY, A CORPORATION OF NEW YORK.

ALTEBNLTINMUBRENT MOTOR.

Specification of Letters Patent.

Patented Doc. 3, 1907.

- Application filed December-18. 1905- Bsrial lilo. 293.129.

To all whom it may concern:

Be it known that I, Flui-zmucn Eicnaaao, a su hjcct of the Emperor of Austria-Hungary residing at Berlin, Gennany, have invented certain new and useful Improvements in Alternating-(urrent Motors, of which the following is a s wcific-ation. I

My invention relates to the control of altcmaling-curreut motors of a type described in former applications filed by G. \Vintcr and myself, in which the armature is provided with a commutator and brushes which shortcircuit the armature on the line of rimary magnetization, while a field is prm need in the motor by suitable connections from the source of current to points displaced ninety electrical degrees from the line of primary magmetization and the armature short-cit cuit. These connections may be made through brushes bearing on the commutator displaced ninety electrical degrees from the short-eircuiting brushes, or they may be made to oints similarly positioned on the stator wmding. The particular arrangement of these connections for producing the field at right-angles to the line of the armature short-circuit is immaterial as regards my resent invention.

it y invention relates to starting motors of this ty e. I have found that while small motors 0 this type may be connected directly to the source while at rest, this method of starting in the case of large motors produces a heavy current-flow, since at startlng there is no counter-electromotive force of rotation but only of self-induction, so that the armaractically to shortcircuit the rimary win at the points of suppl an consequently auxiliary devices must relied upon for preventing excessive flow of current.

My invention consists in starting motors of this type by producing a displacement between the line of primary magnetization and the armature short-circuit. As a result of this displacement the short-circuited portions of the armature are not in inductive relation to the entire primary winding and the remaining ortions of the primary winding serve as in uctances to keep down the starting current. At starting the connections for supplying the field disp aced ninety degrees om the armature short-circuit may either be left closed or be broken. Then when the motor is up to speed these connections if open are closed and the primary magnetization and armature short-circuit are brought back into line with each other.

My invention will best be understood by reference to the accompanying drawing, which shows diagrammatically one arrangement of a )paratus with which a motor may be controlled in accordance with my invention.

111 .the drawing A represents the stator phase source. through the switch S.

B represents the armature which is provided with a connuutator C and two sets of commutator brushes. One set I) b is connected to short-circuit the armature on the line of primary magnetization, while the other set I) is displaced ninety degrees from the firstset, and is connected to a suitable source of current for producing a field in the motor displaced substantially ninety degrees from the line of primary magnetization and the armature short-circuit. The source of current for this cross-field is shown as a transformer T, the primary of which is in circuit with the primary motor circuit, while the secondary is connected to the brushes 1) b. By means of a switch 8 laced in the secondary circuit of the trans ormer the connections for roducing the cross-field in the motor may he broken. The stator winding A in addition to the usual set of taps in line with the armature brushes b b, has a second set of taps displaced from this line and connected to one side of the doublethrow switch S. When the switch S is, thrown so as to connect these auxiliary terminals to the line the primary magnetization is displaced from the line of the rotor shortcircuit and the motor will accordi 1 start like an ordina repulsion motor. The portion of the win i ,i. e.-the portion between the auxiliary starting terminals and the line of the motor brushes is not in inductive relasequently these rtions act at starting as ,in uctances in t e primary circuit to keep down the flow of primary current. Since the motor starts as a repulsion motor, the cross-field is not required, and consequently the switch 8 may be open at starting so that the primary of transformer T acts as a chokecoil in the motor circuit to reduce further the starting current. Of course, if the secondary circuit of the series transformer is to be thus tion to the short-circuited armature, and conwhich is adapted for connection to a singlewhen open-circuited.

broken at starting, the transformer should be so designed as not to produce an excessive -rise of voltage. at the secondary terminals After the motor is up to speed the switch .9 is closed, it it has been opened at starting, and the switch S is thrown over to its other position so as to connect the source of current to the main rimary terminals in line with the armature Srushes I) b. The motor then operates in the usual manner.

It is obvious that it makes no difference in the operation of the motor whether the displacement between the primary magnetization and armature short-circuit at starting is obtained by shifting one or the other. In other words the effect produced is exactly the same if, instead of shifting the points of connectionof the source to the primarywinding, the armature brushes are shifted. Consequently my method of control maybe carried out in either way.

What I claim as new, and desire to secure by Letters Patent of the United States, is,

l. The method of operating a single-phase motor of the commutator type which consists in starting the motor by short-circuiting the armature through brushes displaced from the line of primary magnetization and supplying to the armature through brushes displaced substantially ninety electrical degrees from the short-circuiting brushes a-current adapted to produce a magnetic field displaced from the primary ma metization and after the motor is up to spew bringing the armature short-circuit and primary magnetization into 2. The method of operating a single-phase motor of the commutator type having two sets of brushes displaced from each other by approximately ninety electrical degrees, which consists in starting the motor by shortcircuiting the armature through one set of brushes one line displaced from the primary magnetization and supplying to the other set of brushes current adapted to produce a field displaced from the primary magnetization and after the motor is up to speed bringing the armature short-circuit and the primary'magnetization into line.

In witness whereof, I have hereunto set my hand this twenty-firstday of November,

FRIEDRICH EICHBERG.

Witnesses:

VOHUN SINGER, MAX IIANDLEY. 

